Probiotics, live microorganisms that, when administered in adequate amounts, confer a health benefit on the host, offer an alternative to antibiotics and have become popular among shrimp farmers for use in the regulation of pond water quality, promotion of shrimp growth and the prevention of disease. Most shrimp probiotics are selected for testing based on their ability to competitively exclude pathogens through bacterial antagonism assays, although the mechanisms of pathogen exclusion are rarely investigated. In this review, we provide a comprehensive overview of the mechanisms of competitive exclusion (interference and exploitation competition) by species screened and subsequently identified as shrimp probiotics based on their ability to inhibit the growth of pathogenic bacteria in vitro. We show that the current methods used to identify potential probiotics preferentially select for interference-based competitive mechanisms and may overlook the potential of many species to be considered a probiotic. Furthermore, we show that the efficiency of a probiotic in vivo may be improved by considering the suitability of competitive strategies to shrimp farming conditions. We highlight important limitations and future directions for the screening and identification of probiotics in shrimp aquaculture, to aid in the development of effective and sustainable microbial management strategies.

Amplicon sequencing on a High Throughput Sequencing (HTS) platform (custom barcoding) was used to detect and characterise myxosporean communities in environmental DNA samples from marine and freshwater environments and in faeces of animals that may serve as hosts or whose prey may host myxosporean infections. A diversity of myxozoans in filtered water samples and in faeces of piscivores (otters and great cormorants) was detected, demonstrating the suitability of lineage specific amplicons for characterising otherwise difficult to sample parasite communities. The importance of using the approach was highlighted by the lack of myxosporean detection using commonly employed, broadly-targeted eukaryote primers. These results suggest that, despite being frequently present in eDNA samples, myxozoans have been generally overlooked in 'eukaryote-wide' surveys. Lineage-specific primers in contrast detected 107 OTUs that were assigned to both the "freshwater" and "marine" myxosporean lineages. Only 7% of these OTUs clustered with sequences in GenBank, providing evidence for substantial undescribed myxosporean diversity. Many new OTUs, including those found in otter faeces, clustered with a clade of myxosporeans previously characterized by sequences from invertebrate hosts and water samples only. Because myxozoan species identification is highly reliant on molecular signatures, lineage-specific amplicon sequencing offers an effective and non-destructive means of improving our knowledge of myxozoan diversity. In addition, the analysis of myxozoan DNA in faeces of piscivores offers a potentially efficient method of sampling for diversity and revealing life cycles as piscivore activities may integrate myxozoan infections in fish over relatively broad spatial scales. *Graphical Abstract (for review) Highlights eDNA reveals diversity across the myxosporean phylogeny in water and faecal samples  A custom barcoding approach amplifies myxosporean SSU rDNA that is missed in 'eukaryote-wide' surveys  Piscivore activities may be useful in integrating myxozoan infections in prey over broad spatial scales  Recommendations for assessing the presence of myxozoans in eDNA are provided AbstractAmplicon sequencing on a High Throughput Sequencing (HTS) platform (custom barcoding) was used to detect and characterise myxosporean communities in environmental DNA samples from marine and freshwater environments and in faeces of animals that may serve as hosts or whose prey 25 may host myxosporean infections. A diversity of myxozoans in filtered water samples and in faeces of piscivores (otters and great cormorants) was detected, demonstrating the suitability of lineage specific amplicons for characterising otherwise difficult to sample parasite communities. The importance of using the approach was highlighted by the lack of myxosporean detection using commonly employed, broadly-targeted eukaryote primers. These results suggest that, despite being 30 frequently present in eDNA samples, myxozoans have been generally overlooked in 'euk...

Breeding ground food availability is critical to the survival and productivity of adult birds. The common cuckoo Cuculus canorus is a brood-parasitic Afro-Palearctic migrant bird exhibiting long-term (breeding) population declines in many European countries. Variation in population trend between regions and habitats suggests breeding ground drivers such as adult food supply. However, cuckoo diet has not been studied in detail since before the most significant population declines in Europe began in the mid-1980s. 20th century studies of cuckoo diet largely comprised field observations likely to carry bias towards larger prey taxa. Here we demonstrate the potential value of 1) using high-throughput DNA sequencing of invertebrate prey in faeces to determine cuckoo diet with minimal bias towards large prey taxa, and 2) using crowd-sourced digital photographs from across Britain to identify lepidopteran cuckoo prey taxa during recent years post-decline (2005-2016). DNA analysis found a high frequency of Lepidoptera, including moths of family Lasiocampidae, prominent within the past literature, but also grasshoppers (Orthoptera) and flies (Diptera) that may be overlooked by field observation methodologies. The range of larval lepidopteran prey identified from photographs largely agreed with those previously documented, with potential signs of reduced diversity, and identities of key adult prey taxa were supported by molecular results. Notably, many identified cuckoo prey taxa have shown severe declines due to agricultural intensification, suggesting this has driven spatial patterns of cuckoo loss. Landscape-scale, lowland rewilding interventions provide opportunities to understand the scale of reversal of previous agricultural intensification that may be necessary to restore prey populations sufficiently to permit recolonization by cuckoos.

The spread of disease is widely recognised as a significant hazard for biodiversity and human health (Sutherland et al., 2020) and is frequently linked with climate change (Hoberg & Brooks, 2015).Mechanisms that mediate disease emergence and spread include globalisation of human activities and changing phenologies, distributions and behaviours of disease vectors (Fong, 2017;Lafferty, 2009).However, movements of animals may also generally facilitate the codispersal of hitchhiking parasites and pathogens.Many organisms can achieve dispersal by surviving passage through the gut of animal vectors. The majority of such research in